The proposed research deals with the purification and characterization of low molecular weight (MW) selenium containing proteins from ovine tissues, the distribution of selenium between different MW proteins in cytosols from tissue of lambs of different selenium status, determine the return of calcium uptake ability and ATPase activity of sarcotubular reticulum vesicles (SRs) after injection of white muscle diseased (WMD) lambs with selenium or vitamin E, and study the incorporation of 75Se from selenite or 3H from alpha-tocopherol into SRs of lamb muscle. Low MW selenium containing proteins will be purified by ion exchange and gel filtration column chromotography from tissues of lambs injected with 75Se-selenite, and their amino acid composition, selenium content, species of selenoamino acid present in these proteins, and amounts of Se-protein in relations to incidence of WMD determined. 75Se will be injected into WMD lambs, WMD or normal lambs fed marginal levels of selenium, and lambs fed high levels of selenium, and the distribution of selenium between different MW proteins in tissue cytosols determined by gel filtration. The protein which increases to the greatest extent upon high dietary selenium exposure is planned to be purified and characterized. All proteins are proposed to be purified with respect to selenium, but derivatives of them will be prepared if deemed necessary to aid in the purification efforts. Muscle biopsy experiments are planned to investigate the return of calcium uptake ability of SRs from WMD lambs after selenium or vitamin E injection. The SRs from biopsied muscle will be assayed for calcium uptake ability and ATPase activity, subjected to sodium dodecylsulfate polyacrylamide gel electrophoresis, and centrifuged on sucrose density gradients to separate the light and heavy vesicles. Lambs will be injected with 75Se-selenite or 3H-tocopherol and the incorporation into SR membranes determined. IDEN*